1. Field of the Invention
The invention relates to a method for controlling illumination devices of vehicles, preferably motor vehicles, in which the illumination devices are correlated with different functional areas and are supplied with current. The invention also relates to a device for performing such a method, wherein the device comprises illumination devices correlated with at least two functional areas which are connected to an electrical power source and can be switched on by actuating elements.
2. Description of the Related Art
It is known in regard to tail light assemblies of a motor vehicle to assign various signaling functions to the illumination devices. The tail light assemblies, comprise generally a tail light, a brake light, a rear fog light, and a reverse drive light. It is known to use LEDs as illumination devices for these purposes. LEDs require low electrical current, for example, 20% of the rated current or less. In this range, the LEDs have great tolerances with respect to the forward voltage. This results in the LEDs being illuminated with different brightness, depending on the manufacturing tolerances.
It is an object of the present invention to develop the methods and the device of the aforementioned kind such that the brightness of the illumination devices can be adjusted in a directed manner.
In accordance with the present invention, this is achieved with respect to the method in that the illumination devices are cycled with the rated current and their brightness is adjusted by a pulse width modulated signal.
In accordance with the present invention, the object is achieved with respect to the device in that the actuating elements are connected to at least one microprocessor which converts the signals of the actuating elements into pulse width modulated signals which are supplied to the output terminals of the microprocessor and can be supplied via driver stages to the illumination devices.
Accordingly, the illumination devices are cycled with the rated current and their brightness is adjusted by pulse width modulation for compliance with the legal requirements. The illumination devices are advantageously LEDs but can also be incandescent light bulbs. The pulse width modulated signals are generated in the microprocessor and are supplied via the drivers stages to the respective illumination devices. The brightness change is realized by a pulse width modulated signal which is generated in the microprocessor by means of a corresponding program. In the case of LEDs being used as the illumination devices, they can be controlled with minimal current supply reliably such that the legally required brightness is provided for the each signal function, respectively.